Such a machine tool is described in FR-A-2 715 336, of which the Applicant is proprietor.
In that document, the carriages are disposed on opposite faces of the cross-member and the section of the cursor-carrier in a plane perpendicular to the Y axis is U-shaped defined by two parallel flanges interconnected by a web disposed beneath the cross-member, the two flanges being slidably mounted on the opposite faces of the two carriages.
That U-shaped configuration of the cursor-carrier gives rise to mechanical deformation which is harmful for machining accuracy, particularly when the distance between the flanges is designed to make it possible to move the spindle a long way along the X axis without moving the gantry. To remedy that problem, it is necessary to increase the dimensions of the cursor-carrier, thereby increasing its weight, which gives rise to an increase in the inertia of the moving parts, and thus to a decrease in displacement speed.